Centrifugal hydraulic pump



Jan. 25, 1955 c. A. scHELLENs CENTRIFUGAL HYDRAULIC PUMP 3 Sheets-Sheetl Filed July 29, 1950 Jan. 25, 1955 c. A. scHELLENs CENTRIFUGALHYDRAULIC PUMP 3 Sheets-Shea?l 2 Filed July 29. 1950 INVENTOR BY s www,NM g Mh, ATTORNEYS Jan. 25, 1955 c. A. scHl-:LLENS CENTRIFUGAL HYDRAULICPUMP 3 Sheets-Sheet 3 Filed July 29. 195o INVENTOR C, Q Swonw ATTORNEYSmm u.. v

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CENTRIFUGAL HYDRAULIC PUMP Christopher A. Schellens, Tenants Harbor,Maine Application July 29, 1950, Serial No. 176,599

2 Claims. (Cl. 10S-112) This invention is a novel centrifugal hydraulicpump of the general class wherein a shaft-borne impeller or runner ispower-rotated, as by a turbine, within a closed casing wherein theimpeller receives, as through an inlet conduit, the water or otherliquid to flow through the inlet to the impeller eye or entrance spacesurrounding the axis of rotation. The liquid by a circular series ofimpeller mouths enters the centrifugal flow passages and, by the forcingaction of the impeller rotation, ows outwardly for eventual discharge,by way of peripheral outlets leading to a delivery conduit for use ordisposal.

This invention pertains especially to that well known type of pumpswherein the enclosed impellers are laterally closed, havinguninterrupted sides or bounding walls extending between the impellerinlet openings and the outward discharge openings, and rotating with theimpeller, without contact between casing and impeller. In such types theimpeller outward ow passages, usually of approximately oblong section,are entirely internal, constituting channels which usually extend from acentral axial path near the inlets with gradual change of direction ofsmooth curvature for outward iow and nal delivery in planes extending atright angles to the general or rotary axis of the pump. The presentinvention pertains to the laterally-closed impeller type of rotaryimeller.

p An underlying problem to which the present invention is directedrelates to the very common existence of factors causing seriousdifferential pressures upon the closed opposite sides of a high speedpump impeller, the differences between which pressures tend to thecreation of a very substantial resultant axial pressure, in onedirection or the other, upon the impeller and pump shaft. Variousfactors are responsible for these inequalities of liquid pressure andthrust, and in all cases there is a strong tendency to harmfulmechanical results in respect to the shaft bearings, especially thethrust bearings thereof which, under varying or constant substantialendwise thrust become impaired by wear and suffer incerased cost ofmaintenance, to a highly objectionable extent.

The drawings Fig. 1 is an axial or longitudinal radial section, partlyin elevation at the driving end, of an illustrative centrifugalhydraulic pump of the conventional single-eye or one-inlet type, as afirst form, embodying the present invention; and the ligure forconvenience may be considered a vertical section, in cases wherein thepump is installed to discharge upwardly, which is not a necessarylimitation.

Fig. 2 is a left end elevation showing in face view the impeller of Fig.l, detached from other parts of the pump, and partly cut away to showthe interior passage and blade structure.

Showing a second form, in Figs. 3 to 6; Fig. 3 is a left end elevationof a modified and improved impeller which is particularly adapted tofull utilization of the benefits of the invention and overcomes certainlimitations which are encountered in the application of the invention tothe impeller shown in Figs. 1 and 2; the Fig. 3 impeller being showndetached from the pump, looking into the single inlet or eye thereof,and broken away to show certain interior construction; the impeller ofFigs. 3-6 being adapted to use in various types of hydraulic pumpincluding that of Fig. l; the illustrated impeller resembling in generalprinciples that shown in ited States Patent() Mice applicants expiredprior Patent No. 1,664,488 of 1928, but supplemented by the novelfeatures of the present invention.

Fig. 4 is a transverse vertical sectional View of the impeller of Fig. 3taken on the section line 4 4 of Fig. 3; Fig. 4 like Figs. 3 and 5affording a true rather than a mere conventional showing of the flowpassages, the enclosing side walls and the interior metal portions orpartitions which define such passages.

Fig. 5 is an underneath or inverted plan View of the impeller of Figs. 3and 4.

Fig. 6 is a detached view of a structural detail, taken in section onthe section line 6 6 of Fig. 3.

Fig. 7 is a central vertical section of a two-inlet or double-eye pump,having passages of the same general form as in the impeller of Fig. 3,and following in general the pump of that type illustrated in the priorpatent of this applicant, No. 2,101,653 of 1937, but reconstructed andmodified to embody the principles of the present invention.

Fig. 8 is an end elevation or righthand face view of the impeller per seillustrated sectionally in Fig. 7.

First form, Figs. 1 and 2 Describing first the conventional portions(considered without the present improvement) of the hydraulic pump shownin Figs. 1 and 2, at the front end of the system, being the left end ofFig. l, is the pump casing 10, 11, consisting of a fixed casing part orbody 10 and the complementary front head or cover part 11 bolted on.

The casing head 11 is formed with an inlet conduit 12 delivering axiallyinto the entry spaces of the impeller. The casing body is similarlyformed with a conduit 13, providing the final outlet delivering from thepump discharge chamber 14 for any desired use or destination. Whilereferring to the casing parts it is here explained that the body 10 isprovided with a closed intermediate extension 16, while at the rear orrighthand end of the apparatus, is a closed rear casing 17, connectedwith casing 16 and containing a suitable driving motor, such as theindicated turbine motor 1S. A central shaft 19 is turned by the motorand is unitary with or coupled to the shaft which carries the impelleror runner element 25 to be described. This shaft 19 operates in ball orroller bearings 20, 20 which, taken separately or in cooperation mayserve also as thrust bearings, intended to resist axial or endwiseshiftings, and being vulnerable to excessive thrust action.

The water or other liquid is brought to the pump conduit 12 by anydesired exterior conduits or pipes, leading from a source of hydraulichead or liquid supply providing the necessary initial pressure, whichmay be low or high. There is diagrammatically indicated a supply 21.,fed from any available source, and delivering through piping 22 into theinlet conduit. As a preferred auxiliary detail a pipe 23 is shownleading from one of the pump leak chambers 59, to be described, aroundto where the escaping liquid is delivered freely into the relativelylzolw-pressure inlet 12, either directly or by way of supply Theillustrated pump, according to conventional practice, has an entrancespace 24 called the eye of the pump, being that completely circularportion of volume or space through which the ow passes from the conduitj 12 into the impeller 25. The impeller is a preferably one-piece rotarymember driven at high speed from the shaft 19. One customary partof'such an impeller is a central and frontwardly extending portion,'designated a crown, projecting into the eye-space 24 and therebyassisting to dene the annular flow from the inlet into the impeller owpassages 30, to be described. The crown is shaped with a rounded nosefollowed by smooth outcurves toward the spaces and enclosing walls ofthe irnpeller; the crown in this way causing an outswinging tiow of theentering liquid, minimizing obstruction and turbutube being threaded forsecuring purposes and keyed to the shaft 19.

The set of six iow passages 30 of the impeller receives and delivers themain oW of liquid through the irnpeller, from the receiving centralportions to the outward discharging portions, and the passages aredisposed Spirally therebetween to receive eicient centrifugal pressureand velocity toward and beyond the discharge. The ow within theoperating part of the impeller is from the eye 24 or the circularlyaligned six mouths 3S therebeyond, along the spiral paths to theperipheral discharge outlets 36; and these flow passages are bounded anddeiined, in their axial dimensions, by the rear and front outer impelleiface parts or Walls 3l and 32, and transversely by the disposition ofthe interior metal portions or separators 34 between those walls, forexample, in the form of blades as shown in Fig. 2. Between 24 and 35 theow surrounds the crown.

The impeller rear wall 31 and the similar opposite front Wall 32 areclosed annular walls between which the outflow occurs. The rear wall 31and its inside face extend inwards substantially in a plane transverseto the axis, continued thus until the face takes a curve front- Wardlyas it merges into the curvature of the crown 27. Analogously theopposing front wall 32 extends within a transverse plane in a directiontoward the axis, as about 90 thereto, its portions approaching the axistaking a frontward curvature terminating in a substantially axialdirection. As clearly shown in Fig. l, the general disposition of theimpeller front and back walls is such that each passage between themtapers progressively from the inlet eye 24 and thence through the mouths35 into the radially or spirally outward extension of the passage. Wherethe metal of the impeller front wall 32 is shaped with a curveterminating frontwardly there is preferably employed a conventionalimpeller extension 33, attached or screw-threaded to the front wall 32and itself being extending frontwardly in line with the termination ofthe front wall, thus atfording a renewable eye-sleeve adapted to bereplaced when impaired.

Between the unitary rear and front impeller walls 31 and 32 are arrangedthe interior metal portions, in this case shaped of blade form, whichserve to separate from each other the outwardly trending flow passages30. These interior metal parts, between the closing walls, may takevarious shapes and may be considered as impeller portions which deiine,in one dimension, the sectional shapes, usually oblong, and progressingcontours, of the separate flow passages; each such passage commencing atthe mouth line 35, whereat the otherwise annular ow is divided into sixstreams by the interior portions or spiral blades, and continuing to theimpeller peripheral discharge points 36. Further features and details ofthe impeller itself will be hereinafter further described and explained.Each blade begins at its nose 34a and ends at its tail 34h.

Referring to some of the adjacent and associated elements, Fig. 1 showswithin the casing, between its rear wall and the impeller, aconventional diaphragm 38 or removable annular supporting member, shapedat its front or inner side to clear the rotating impeller where theseparts face each other; and this diaphragm 38 is formed with an upwardextension 39 reaching beyond the exit line 36 at the extreme peripheryof the impeller. Similarly there is a front xed annular diaphragm 41mounted on the casing cover l1 and shaped to face the front side of theimpeller, without contact; with an outward extension 42 reaching beyondthe impeller discharge exits. The two diaphragms have their upperextensions facing each other and spaced somewhat apart to leave anoutward flow space therebetween through which the impeller discharges,in a conventional way, these extensions further acting as supports for asystem of cross walls or guides 43 known as ditfusers, in the nature offixed vanes controlling the onilow of the discharge liquid issuing fromthe impeller.

Throughout the structure it is an aim to minimize metal contact betweenrelatively movable parts. Accordingly the extreme peripheral impellerportions are out of running contact with the diaphragm and extensions,the latter indeed being spaced beyond the impeller rim thus leaving anappreciable free clearance or flow gap 45. At the front side of theimpeller there is a similar but not necessarily equal clearance gap 46between the front wall 32 and the diaphragm extension 42.

This arrangement permits constant and substantially unrestrained backtowof pressure liquid, through these clearance gaps or gates 45 and 46,which are of ample size to obviate appreciable drop of pressuretherethrough, and, in this instance, into relatively wider clearancespaces 47 and 48 constituting chambers existing by reason of the designof the diaphragms where they face the impeller rear and front walls.Liquid escaping from the discharge by the clearances 45 and 46 enter thechambers 47 and 48, flowing toward the axis, under the high pressure,for eventual restriction and release, as by control rings. Other backowsor leakings, if any, at both sides of the impeller, may be similarlycontrolled.

To prevent undue back leakage and escape of high pressure liquid fromthe discharge chamber i4 a system of control devices, acting as wearingrings, is conventionally provided in this class of hydraulic pump. Thus,a first or front wearing ring 50 is shown, mounted in a ixed position onthe casing head 11, and adjacent to but slightly out of Contact with therotary eye-sleeve 33. This pair of annular elements 55, 33 constitute acouple for control purposes, the fixed one being deemed the wearingring. As the sleeve is a renewable extension of the impeller front wallthe object is attained of minimizing backilow through the several spacesafront the impeller which directly or indirectly receive from thedischarge chamber i4. The wearing ring 50 seats tixedly against anannular block 51, both located within a recess in the casing head. Thering and sleeve cooperate by means of a labyrinth structure, in thiscase provided on the ring, as shown in Fig. 1. This arrangement,hereinabove described, is known as a hard rather than a soft packing.Water escaping the labyrinth ring 50 passes into the lower pressure ofthe pump inlet.

Just as the eye sleeve 33 serves as a front extension of the impellerfor wearing ring purposes, so also the back extension, block or hubsleeve 53 serves as an impeller extension for the same purposes. Thereis shown first the xed or labyrinth ring 52 mounted in a seat in thefixed diaphragm 38, this ring being just out of contact with the annularhub sleeve or block 53 rotating with and being a rigid part of theimpeller by its seating in a recess of the impeller. Leakage occursthrough and beyond this wearing point, where there is provided asupplemental or soft packing ring 54 occupying a threewalled chamber 54awhich extends from the diaphragm 38 inwardly to the exterior surface ofthe impeller hub extension 28, or rather to a smooth sleeve 29 threadedupon 28, and turning within the packing. The function of the soft ringis to seal the shaft at this point against leakage. The aforesaid hardWearing rings 5@ and 52, when the pump pressure is not extremely high,and where there is consequently no appreciable unbalanced axial thrustdue to pressures acting on surfaces diametrically within the wearingrings, may be both of the same diameter, as shown, but I may preferunder other conditions to employ slight differences in the Wearing ringdiameters.

The two sleeves 33 and 53, at front and back, being equal in diameter itwill be readily seen that (provided the water supply at the inlet 12 isof a pressure substantially or slightly above atmosphere, and providedthe turbine exhausts at a pressure substantially equal to or slightlyabove atmosphere), there exists no unbalanced axial force due topressures inwards of the Wearing rings, that is, of the clearancesthereof, at the two sides. Under other circumstances other well knownmeans would be provided for balancing the thrust due to pressures inthese regions, but these regions and these means form nro part of thisinvention and will not be described furt er.

Further reference is here made to the clearance or back-flow spaces andchambers, and their operation, commencing with the already mentionedchambers 47 and 4S bounded respectively by the impeller closing walls 31and 32; with which should be mentioned again the gaps or escape gates,channels or spaces 45 and 46 by which the discharged liquid, under highpressure, may pass into the chambers 47 and 48; the portions of whichliquid that are nearest to the impeller periphery may exist in asubstantially balanced condition owing to the short free communicationsfrom the discharge chamber 14 through both of the gaps 45 and 46 intothe chambers 47 and 48, Each of these chambers is outwardly bounded byone of the diaphragms 38 or 41 the latter of which is held in place by aconnecting joint 55. Frontward of the diaphragm is another space 56existing between the diaphragm 41 and the extension of the casing head11, but this contains only dead liquid. The described escape chambers 47and 48 are constantly full of liquid and under constant receipt ofliquid passing from the high pressure point for flow inward toward thegeneral axis of the pump.

Between the chambers 48 and 56 stands the diaphragm 41, extendingradially toward the center for substantially the same extent as theimpeller walls 31 and 32 but in a way to leave an intercommunication 57,on the way to the wear ring 50. This local system of escape flowclearances or chambers extends to and terminates at the wear ringclearance which forms the leak-restraining element separating thedischarge spaces from the entrance spaces of the impeller. This actionreleases in negligible quantities the escaping liquid into the generalinlet 12, for recirculation.

Thus the escape chambers to the front of the impeller deliver theirleakages back into the general inlet; and the same principles areprovided in respect to the impeller and associated parts extendingrearwardly. Thus the rear clearance chamber 47, receiving directly fromthe discharge chamber 14, extends adjacently alongside the impeller rearwall 31, and inwards thereof extends further toward the axis to reachthe labyrinth packing between the rear ring 52 and the annular wear ringsleeve 53 turning with the impeller. Thus all leakage to the rear of theimpeller hub traverses the wear space between 52 and 53, this smallproportion of liquid passing thence into a system of annular chambers 5Sinside of the rear diaphragm 38, from which it issues into a finalenlargement 59 of chamber 58, from which the liquid may be allowed torelease freely into the pipe 23, already mentioned, which conducts thissmall quantity of escape liquid back directly or indirectly to the inletconduit 12 of the pump.

The present improvement will next be explained, on the basis of theexample shown in Figs. l and 2. g

To disclose specifically this improvement, it involves the modifying ofthe impeller by forming therein the series of cross-ducts 60, eachextending from one side to the other, the same being extended internallybetween the impeller closing walls but issuing at the opposite sidesfrom such walls. These cross-ducts 60 are wholly isolated from the flowpassages 30 but constitute communications between the clearance channelsand chambers which receive the leakage liquids passing back to the frontand rear of the impeller. Within-the impeller, between its side walls,the cross ducts are preferably extended through the interior metal whichprovides at the same time the blades or other partitions, defining theflow passages. Each of the ducts might be afforded by means of a metaltube inserted and extended through the impeller, issuing at the back andfront closed sides; and the interior tubes could be arranged partly orwholly in immersion within the flow passages. v

If the ducts be too near to the general axis, that is, inwards of thewearing rings, they will not perform the functions characteristic of thepresent invention; and they will have no utility if placed too near theimpeller periphery, at which point the leakage liquid, received at thetwo sides direct from the discharge chamber is already reasonablybalanced.

For the purposes of the invention therefore the construction may be setforth as follows: the group or set of cross-ducts is to be locatedwithin an annular region or zone, between larger and smaller zonecircles or boundaries, the larger being well inwards of the peripheraloutlets, and the smaller circle being somewhat outwards of the clearanceor restriction lines of the wearing rings, e. g. the lines of thelabyrinths or of the clearance of the largest wearing rings, at the twosides. The cross-ducts 60 are in an intermediate position located inthat Zone at a point which is considerably nearer, radially speaking, tothe wearing ring than to the impeller outlet. In other words, the ductseries should be somewhat outward of the ring but preferably as closethereto as feasible.

The series of cross-ducts should present in the aggregate an ample crosssection or area, sufficient to afford free and rapid liquidintercommunication and transfer between the opposite, or front and back,clearance spaces,

thus to insure practically instant response to any tendencies arising tocause differential pressures upon the projected areas of the oppositesides of the impeller. If there is a constant tendency for excesshydraulic pressure at the impeller front side, the equalizing ow throughthe ducts 60 maybe steadily to the rear, and vice versa; or the flow maybe oscillating, frontwardly and backwardly, irregularly or periodically.

The ducts are preferably straight but can be otherwise; and they may beround ducts or otherwise. They may pass through the impeller interiorpartitioning metal, as shown, or through small tube lengths inserted totraverse such metal and/or the ilow passages. The ducts may be in asingle series of spaced positions or may be in pairs or multiples.Wherever more free communication is desirable the ducts may be enlarged,with thickening of the interior metal portions to accommodate them. Nodifferential in the frontward and rearward liquid pressures axially uponthe impeller can exist more than momentarily.

With a conventional pump and impeller the partition walls, which mayconstitute blades, may have blunt nose edges at the entrance mouth line,as shown; but in special cases, as where very hot water, approaching itsboiling point, is to be pumped, and especially where substantialhydraulic suction exists at the inlet, the partition metal may not beconstructed with very blunt entrance edges or blades, such as in Fig. 2shown, for ebullition then tends to occur, with cavitation and abreakdown of pumping action. The second form hereinafter describedillustrates a special structure of a hot water rather than a cold-waterpump. In ordinary cases, with no high suction or temperature theconventional type of impeller is satisfactory. In either type theequalizing means of this invention is of substantial utility.

Second form, Figs. 3 to 6 This form, provided'with cross-ducts 61 on theprinciples described, is of value both for pumping Water under thefavorable conditions specified for Form 1 and for cases wherein thetemperature and/or suction are high enough to cause the describeddifficulties with Form l, due to foaming behind the blunt noses of theblades near the impeller entrance mouths. The impeller of Form 2 in itsinterior structure is wholly different from Form l, and while each haspartitioning metal defining passages, Form 2 eliminates definite bladeswhose blunt entrance edges would generate cavitation with hot liquid andsubstantial suction.

In the second form the separation of the ow into streams starts furtherback and near to the main inlet, so that each passage begins near theeye with helicalaxial flow, the mouth-separating metal here being thinand sharp, cutting the ow into the six separate helical passages withoutincurring the diiculties of Form l; the flow direction then smoothlyswinging outward and entering the general impeller outflow in the formof six separate and substantially spiral passages, until reaching thecommon exit line 74. This manner of construction is in principlesubstantially like that disclosed in the aforesaid prior Patent No.1,664,488, Fig. 2 of which may be compared with Fig. 4 herein. Thecavitation defect is avoided by the employment of the helical-tospiralpath and flow through each of the several passages together with thesmooth-cutting of the sharp character of the mouth edges.

There are in Form 2 no individual blades in the sense of Form l; but theinterior metal portions between the impeller sides (considered as thinsurface metal layers serving as closing walls) are formed as partitionsspecially shaped solely to provide the described axially progressing andthen outtrending passages; and the only parts comparable to blades beingthe thinning parts of the separating metal to afford sharp or knifeedges at the intakes and discharges. In Form 2 the interior metal partsat the entrance mouth line 72 should have their passagedefining faces ata small mutual angle where they intersect at the eye as indicated inFig. 6; and yet, further along, the partitions between passages must beof substantial thickness, to accommodate the balancing crossducts 61.These conditions being practical, as shown in Figs. 3-6, this type ofstructure is particularly suitable for pumping operations wherein,within the important zone de'ned, the tendency to unbalance of pressureson the impeller front and back sides is neutralized by the balancingeffect of the cross-flow through the ducts 61 between the front and backouter sides of the impeller.

Referring to the details of Figs. 3 to 6, the cross-duct feature 61 isembodied in the impeller 65, shown per se; it being understood that theimpeller is to be operated within a casing and associated with otherparts, for example of the character illustrated in Fig. l. Thus, it isto be understood that the cross-ducts 6i lead to and from clearancespaces existing between the impeller closed sides and the respectiveadjacent diaphragms on the principles ot those designated 3S and d1 inFig. 1'. For explanatory purposes it may be said the pump in which theimpeller 65 is used may have wearing and packing rings like t) and 52and accompanying parts; and other features also may be in common.

The ow passages 7) of the second form are essentially different fromthose of the first form, resulting in different operations and results;each passage starting in the form of an axial helix, this helical formprogressively changing to a spiral form of passage trending outwardlyfor discharge at the periphery. The entrances or mouths 71 of theseveral passages extend from a mouth line or plane 72, from which thecontinued fiow takes place. After traversing the passage entrances andthe main parts of the passages the flow streams reach and take exit bythe peripheral exits .73 arranged in a dis-` charge line 74. Fig. 4indicates a few of the sections of successive ow passage, which show theoblong forms, with corresponding sides shown parallell and perpendicularrespectively to the impeller axis.

For the accommodation of a series of such flow passages the impeller isof a structure described as foilows. The impeller has the closed rearsurface or wall 75 and opposite to it the closed front surface 77. rl`hewall 75 has a curve 76 merging into the crown; and wail 77 a curvefrontward toward the threaded boss 79, which may carry an eye-sleeve.The impeller hub has a tubular back extension 63 by which the impelleris keyed to the shaft; also a threaded boss 69 to receive the sleevebloclf` or collar 53 of Fig. 1. Similarly at the front is a boss 79adapted to receive the eye-sleeve 33 of Fig. 1.

The passages 7i) may be defined as being of substantially quadrilateralsection, Figs. 4 and 5, two of the walls of which are surfaces which aresubstantially helicoidal, the other two being surfaces which aresubstantially spiral, throughout their length; the spiral surfacesextending from the outer periphery of the impeller inwardly with adecreasing pitch terminating at or near the eye, Fig. 3, or the mouthline 72, wherey said pitch becomes zero; and the helicoidal surfacesextending` from the eye to the discharge with a decreasing pitchbecoming zero at or near the peripheral discharge line 74. Apart fromthe shape of the impeller and interior passages, the adjacent elementsof the impeller including wearing rings and associated parts, may be asshown in the first form, Figs. l and 2, and no further description ofthese general elements is deemed necessary. The improved irnpellerconfers on the pump a smooth, continuous fiow action after a similarentrance.

rThe impeller, although preferably a unitary piece of metal, may beconsidered asV composed generally of its closing walls 74 and 76 andinterior thereof other metal portions or partitions 8h, which are not ofthe character of blades except in a broad sense, but which areconfigured to define the passages' and produce the helicalspiral mannerof flow through the impeller. These interior metal partition members arenot simple to describe as such, but may best be referred to asconstituting and occupying the entire interior of the impeller bodyother than the spaces which constitute the six helical-spiral flowpassages. One definite interior partition part may be referred to asinvolving the sharp entrance edges 81, as seen in Figs. 3 and 6. Asshown in Fig. 6, this entrance S1 portion of the' interior metal ismachined away and sharpened, and as well is placed at an acute entranceangle to effect the smooth cutting of the water as it enters and takesup its helical whirl within its passage. The curved dash lines 33represent the boundaries of the respective flow passages, and as well ofthe separating metal portions between such passages, Fig. 3 indicatingthese dash lines and as well the successive passages 7i? and the'separating metal Sti therebetween. This descriptionV makes clear how'ample' interior metal is available for the introduction of thecross-ducts, as by drilling, without in any way disturbing the sharpcharacter of the entering edges of the separating partitions at theimpeller eye. It is also made' clear how there is sufficientlongitudinal extent of interior metal between the balancing holes 61 andthe discharge end of each separating portion S4 between two adjacentpassages= to present a sharp thin edge for the departing liquid, wherebyeddying is avoided.

Since the addition of cross-ducts requires ample thickness at a radialdistance which, in the first or cold-water form, requires the ducts tobe near the entrance edge, it may be impossible there to locate theducts at a radius small enough to function as ducts without greatlyblunting the blade entrance edges as in Fig. 2 shown, thus sacrificingthe advantages of the hot water use of the second form, attained by thechanged construction thereof including the sharp entrance angle of thepartitioning metal in the axial-helical portion of the flow.

Third form, Figs. 7 and 8 The third form, representative of yet otherforms presenting similar problems, is based on the twin-inlet ordouble-eye type of Patent No. 2,i01,653, modified to afford theadvantages of the present invention. lt also has general features incommon with forms l and 2; and specically the three forms constitutepractical embodiments of the invention. Detailed description is deemedunnecessary as said patent may be referred to, along with forms 1 and 2,by way of supplement to the disclosures of this chapter.

While symmetrically duplicated as compared with form 2, the flowpassages of form 3 are definable in the manner above stated for form 2,and the advantages conferred are comparable, each form presents theprovision of thick interior passage-defining metal, very practicallyadapted for the forming or drilling of the equalizing cross-ducts 62, atthe same time allowing the desirable sharpness of the metal edges orblade-like entrances, so important at the infetto obviate the statedinferiority of structure and operation of the conventional bladedimpeller of the first form of the invention.

The third or double-eye form has a circular series of eight spaced apartcross-ducts 62 serving to afford rapid equalization of liquid pressuresat the two sides of the impeller 87.

The" pump of this modification has an upright casing 88, the under partof which encloses an inlet conduit 89, this being branched to supply theliquid in an axial direction to both the lefthand and righthand sides ofthe impeller. This liquidV after traversing the impeller passes into anannular discharge chamber 99'.

The pump impeller is carried on a through shaft 91 by which it isdriven. It has symmetrical annular eyes 92, each leading toward theirnpeller flow passages 93; which are defined by the closed outer layersor walls 94 and 95 at right and left and the specially configuredinterior metal 96. A

The two annular eyes 92 are associated with eyesleeves 97 mounted' onthe impeller, and these precede the actual entrance mouths S. Aftertraversing the eye at each side, and the mouths leading to thehelical-spiral flow passages 93 the discharges occur by way of openings99, of which, at the periphery there may be four and four or eight inperipheral line, delivering to the discharge chamber 90. The spiralportions of the two sets of passages commence well apart within theimpeller but trend toward each other' as shown in Fig. 7, the separatestreams nally issuing peripherally through eight exits distributed inclosely spaced alternating arrangement around the central part of theirnpeller periphery and deliveringfinto the discharge chamber lili.

It is deemed unnecessary to detail the remaining structure of the pumpand impeller, as the patent cited may be referred to, except as to theequalizing feature. Thus the diaphragms, the ow clearances and thewearing rings etc. have been sufficiently described. The usual mode ofconstruction is to provide eight cores, four of them representing thefour identical lefthand flow passages and the other four the righthandflow passages; these cores beingV assembled in the casting mold in amanner corresponding with the desired arrangement of the passages. Thiswill be understood by reference to Forms l and 2 and to said Patent No.2,101,653.

However, attention is called that, corresponding with Forms 1 and 2, thecross-ducts 62y here are arranged in a series o'f eight or' more', withall of the ducts in a zone which is somewhat outward of the wearing orpacking rings, and somewhat inward of the iinal peripheral dischargeexits of the impeller; and, as shown in Fig. 8 these cross-ducts arearranged also to penetrate through the overall thickness of theimpeller, from one outer side to the other, at points which extendwholly through the interior metal portions or partitions 134, so thatwhile cach of the ducts extends through from wall to wall none of themmake communication with the flow passages 130.

There have thus been described illustrative embodiments of the presentinvention for centrifugal hydraulic pumps and the impeller elementsthereof, embodying the principles and attaining the objects of thepresent invention; but since many matters of structure, combination,arrangement, detail and method of operation may be modifed within theessence of the invention, it is not intended to limit the invention tosuch matters except to the extent set forth inthe appended claims.

What is claimed is:

1. In a centrifugal pump having casing means and adapted for pumping aliquid at near its boiling temperature, an impeller formed with acentral inlet eye at one side thereof and having laterally closed owpassages of substantially oblong or rectangular cross sectioncornmunicating with said eye and discharging at the periphery of saidimpeller, each of said passages having two axially and radiallyoutwardly extending helical side walls having a generally decreasinghelical pitch from their entrance to their discharge ends whereat saidpitch becomes zero and Whereat each of said side walls merges to one oftwo surfaces of revolution common to all the said passages, and each ofsaid passages having a radially inner and a radially outer spiral wallof generally increasing spiral pitch from their entrance to theirdischarge ends, said spiral pitch being zero at said entrance endswhereat said spiral walls form exterior and interior cylindricalsurfaces of an impeller eye common to all said flow passages, said owpassages being further characterized by overlapping each other at andnear their entrance ends when viewed from an axial direction, andoverlapping each other at and near their discharge ends when viewed froma radial direction, the axial overlap ceasing at an intermediate point,and a plurality of axially directed cross ducts extending through saidimpeller from side to side for equalzing the liquid pressures on theopposite sides of the impeller, each of said ducts being disposed in thematerial forming the spiral walls of the duct at a location closelyadiacent to but radially outwardly of the point at which the axialoverlap ceases, said cross ducts being free from direct communicationwith the interior of the tlow passages, and said impeller having asubstantial thickness of material between all adiacent flow passages atthe point at which the axial overlap ceases whereby the cross ducts areof sufficient size and are located at a sufficiently reduced radius withrespect to that of the periphery of the impeller to provide for freeflow of fluid through said cross ducts, for effective pressureequalization at opposite sides of the impeller, while the materialbetween adjacent helical side walls of the flow passages provide thinhelical entrance blades such as are required for the pumping of a liquidnear to its boiling point between adjacent passages at their entrance.

2. A centrifugal pump of the class described including casing meanshaving an axial inlet connected with a source of iiuid supply and aperipheral outlet, an impeller with two side walls enclosed therewithinand providing a series of laterally enclosed passages of substantiallyrectangular cross section with central inlets adjacent the impeller axisand peripheral outlets at the impeller periphery with two helical wallshaving a generally decreasing helical pitch from their entrance to theirdischarge ends whereat said pitch becomes zero and whereat each saidside wall merges to one of two surfaces of revolution common to all thesaid passages, and with two spiral walls of generally increasing spiralpitch from their entrance to their discharge ends, said spiral pitchbeing zero at said entrance ends whereat said spiral walls form exteriorand interior cylindrical surfaces of an impeller eye common to all saidflow passages, the passage-separating material being disposed at thepassage mouths to present sharp and thin entrance edges to the inflowingliquid, the said casing means having a peripherally disposed centraloutlet chamber surrounding the said impeller outlets and in iluidcommunication therewith, and said casing means having interior sidewalls forming together with the impeller side walls backow side chambersconnected to receive free flowing pressure liquid from said peripherallydisposed central chamber and direct said flow toward the axis foreventual release, a wearing ring of equal inner diameter on each side ofthe impeller carried by the casing means, rings of equal outer diameterprovided on opposite sides of said impeller, said wearing rings havingclose running clearance with said impeller rings and cooperating withthe impeller rings to form fine circumferentially disposed clearancesbetween the stationary casing means and the rotating impeller on eachside thereof, for restraining the escape of the said liquid, said ringsbeing substantially smaller than the impeller diameter, and saidimpeller periphery at the discharge passage ends having a largeperipheral clearance with respect to said casing means and therebyproviding for the free ow of pressure liquid in passing from the centralchamber to each side chamber, circumferentially spaced orifices passingthrough the impeller from side to side at a diameter slightly greaterthan that of the inner diameter of the wearing rings, said orificesbeing isolated from said laterally enclosed passages to provide freecommunication between the said two backow side chambers, the saidperipheral clearances effecting side wall pressure equalization at andnear the impeller perimeter, and the ducts effecting side wall pressureequalization near the ring clearances, whereby the resultant axialforces due to liquid pressure on the impeller sides exterior of thewearing ring clearances are substantially balanced, and independentmeans connected to said uid supply and to the surfaces of the ringsdisposed at the side of the impeller away from the impeller eye forbalancing the axial forces due to liquid pressure acting on the saidimpeller at points situated diametrically within the said wearing ringclearances.

References Cited in the le of this patent UNITED STATES PATENTS 865,900Hunsaker Sept. 10, 1907 973,782 Hoyton Oct. 25, 1910 1,197,155 SebaldSept. 5, 1916 1,654,907 Wood Jan. 3, 1928 1,664,488 Schellens Apr. 3,1928 1,825,251 Schellens Sept. 29, 1931 2,042,533 Kieser June 2, 19362,101,653 Schellens Dec. 7, 1937 FOREIGN PATENTS 202,042 Germany Sept.24, 1908

